Geodetic mass balance of Abramov Glacier from 1975 to 2015

Abstract

Multi-decadal mass loss estimates are available for few glaciers of Central Asia. On Abramov Glacier (Pamir-Alay, Kyrgyzstan), comprehensive long-term glaciological measurements have been carried out from 1968 to 1999 and re-initiated in 2011. A climatological interpretation of this benchmark glacier in Central Asia requires bridging the gap between historical and renewed measurements. This is achieved here by computing the geodetic mass balance from 1975 to 2015 using previously unreleased Soviet aerial imagery and Pléaides stereo-imagery. During 1975–2015, Abramov Glacier lost 2.2 km2 (8.2%) of its area. The mean annual thickness change was − 0.43 ± 0.14 m a−1 for the period 1975–2015, corresponding to a volume change of − 0.45 ± 0.15 km3. The average specific geodetic mass balance amounts to − 0.38 ± 0.12 m w.e. a−1. The 1975–2015 glacier mass loss lies within the range of glaciological and geodetic mass-balance estimates that were previously published for disparate and shorter time intervals since 1968. This study covers a much longer time period than earlier geodetic estimates and demonstrates the capacity to geodetically constrain glacier change at high spatial resolution in Central Asia using historic aerial imagery and Structure from Motion techniques. Therefore, it could serve as a benchmark for future studies of regional mass change.

Comparison of historical and recent accumulation rates on Abramov Glacier, Pamir Alay

“…Given the trend towards increased net accumulation rates at ~4400 m a.s.l., the slight surface lowering since the 1980s detected based on legacy pictures is not self-explanatory. The observed lowering agrees with the geodetic elevation changes (1975–2015) for this part of the glacier determined by Denzinger and others (in press). The very moderate surface lowering in the accumulation area contrasts sharply with the observed surface lowering of up to 151.3 ± 5.5 m on the glacier tongue (Denzinger and others, in press).…”

“…The observed lowering agrees with the geodetic elevation changes (1975–2015) for this part of the glacier determined by Denzinger and others (in press). The very moderate surface lowering in the accumulation area contrasts sharply with the observed surface lowering of up to 151.3 ± 5.5 m on the glacier tongue (Denzinger and others, in press). The slight surface lowering in the accumulation area may be related to glacier dynamics and/or may have happened in the 1980s or during the period without available observations.…”

“…Our results of increased net accumulation rates for Abramov Glacier, based on in situ data, provide complementary information to local and regional studies based on remote-sensing data and modelling approaches. Whereas the glaciological mass balance of Abramov Glacier has been predominantly negative over the last years, no acceleration of mass loss has been detected (Denzinger and others, in press). No acceleration of mass loss was identified by modelling studies covering the 1999–2011 period without in situ measurements (Barandun and others, 2015, 2018).…”

“…a −1 for the same period (Gardelle and others, 2013). Denzinger and others (in press) computed a geodetic mass balance of − 0.38 ± 0.12 m w.e. a −1 for 1975–2015 and their results indicate that the mass loss of Abramov Glacier has not accelerated recently.…”

Long-term firn and mass balance modelling for Abramov glacier, Pamir Alay

“…Their model is based on a simplified energy-balance approach by Oerlemans (2001). Denzinger et al (2021) computed the geodetic mass balance based on aerial imagery from 1975 and satellite stereo pairs from 2015. Both studies found an overall negative mass balance.…”